The Mobile Internet Protocol (MIP) represents a network-level approach for supporting the mobility of mobile stations across various networks and/or sub-networks. When a mobile station moves from its home network to operate in a foreign network, a home agent associated with the mobile station tunnels data packets destined for the mobile station to a Care-of-Address (CoA) associated with the mobile station. The CoA may be associated with a foreign agent. Data packets destined for the mobile station can then be tunneled to the foreign agent and, subsequently, delivered to the mobile station.
When operating in wireless networks, mobile stations exchange information across data links, which typically operate in a number of modes. For example, the link may operate in a “connected” mode, wherein the data link carries information between the mobile station and access points. In another example, a data link may operate in an “idle” mode, where the link transfers no data. The idle mode allows a mobile station to conserve power by not requiring the mobile station to report its location to the network each time it crosses a boundary of the transmission domain or cell of an access point. Typically, the network is configured so that a group of cells comprise a paging, location, or routing area, and the mobile station is required to report its updated location only upon crossing the boundary of the location area. A mobile station invokes a location update procedure to report its location. Consequently, if the network desires to communicate with the mobile station while in idle mode, a paging message is sent over a wireless interface to a multiplicity of cells, in order to detect the particular cell a mobile station is currently located.
In previous systems, problems occurred as mobile stations transitioned between modes. For instance, if a MIP tunneling agent received new data from a mobile station when the link with the mobile station was in idle mode, new data might not be delivered to the mobile station because the mobile station might move out of the current access point domain during an idle mode, and not report its new location to the agent.
Previous systems also had other limitations. For instance, previous systems often used a central controller to maintain the location information and issue pages to mobile stations. The use of a central controller for paging and processing location updates created addition administrative overhead, increased latency within the system, and generally degraded system performance. Additionally, previous paging and location update schemes were not portable between systems utilizing different technologies, thereby requiring that each system have its own technology-specific implementation.
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